[stella] bipolar joustpong

Subject: [stella] bipolar joustpong
From: KirkIsrael@xxxxxxxxxxxxx
Date: 5 Sep 2003 15:49:47 -0000
After the "sugar high" of a playable alpha and really 
interesting suggestions here on stella list, after trying
my hand at coding last night, I'm sugar-crashing badly.
I'm outta my depth, and now I gotta figure out how quickly
I can learn to swim :-)

So, I focused on a kernal that could support the "Poorlords"
JoustPong variant.  My idea is this: divide the playfield
behind the players into 8 sections (currently of 11 scanlines
each)...then have a byte for each player where 1s were wall 
and 0s were no wall. Then, every 11 scanlines, rotate that byte, 
and see if the negative bit is set...if so, set a buffer for the 
outter playfield nybble to 0010, else 0000, and then set PF0
to the correct buffer at the right time in the scanline.

Well, surprise surprise, even the humblest version of this 
logic (where I set both sides of the playfield to the same 
value, and just toggle that on or off every 11 scanlines)
can set my admittedly sloppyish 2 line kernal well into 
a 2.5 kernal or so, depending on the branching. So I think
I'm in dire need of a kernal rewrite there.

(Honestly right now I don't really understand skipdraw...
but I'll keep pounding through the stella archive via Google.
Sometimes the examples there are tough because it's not 
clear what the variables are...I wish I had a timewarp
to Andrew Davie's AtariAge tutorial on the subject :-)

Also, the collision detection is going to be a bear. I
might have to manually reposition the ball whenever a 
chunk of wall is hit so that it doesn't register double
hits. (Or maybe if I succesfully got the brick removal
in there, it wouldn't be as much of a problem.)

So, questions:
* does this sound like a reasonable implementation
  scheme, with the byte for each player? The bricks 
  are a little tall, but not too too bad.

* Is the search on stella at biglist just plain broken,
  or am I missing something?

* What are the cons to using the "illegal opcode" 
  variant of skipdraw?  and what's the clearest
  example of how to use it?

Many thanks,

KirkIsrael@xxxxxxxxxxxxx    http://kisrael.com
   fight fire with napalm

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